Roller tappet for a fuel pump

ABSTRACT

A roller tappet for a fuel pump is provided that has a guide housing which includes a drive-side and output-side section of the same external diameter, and a separate support body extending longitudinally through the guide housing. An upper face on the drive-side section carries a pin with a roller thereon. A lower face of the output-side section interacts at least indirectly with an arrangement for a pump piston. The guide housing includes a drive-side section and an output side section that are separate, axially spaced rings connected to one another via the support body. The support body has a first ring area with the upper face and a second ring area with the lower face. The first ring area is connected to an inner jacket of the drive-side section and the second ring area is connected to an inner jacket of the output-side section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of PCT Application No. PCT/DE2019/100842 filed on Sep. 25, 2019, which claims priority to DE 10 2018 128 384.9 filed on Nov. 13, 2018, the entire disclosures of which are incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to a roller tappet for an internal combustion engine.

BACKGROUND

A generic roller tappet may be found in DE 10 2017 107 099 B3. The roller tappet is suitable for long installation lengths between pump cams and a following element such as a plunger. However, its complex design is disadvantageous for mass production. The elongated guide housing is in one piece and has a total of three different diameter steps in 5 segments on the outer jacket. On the one hand, the interference fit at the constriction groove of the housing can loosen. On the other hand, this interference fit can influence the high-precision guide surfaces on the outer jacket of the housing, for example in the case of an unfavorable tolerance position. Forming the guide housing by deep drawing requires unnecessary effort because of its length or proves to be almost impossible in the case of particularly long installation lengths to be bridged. Furthermore, it is found that the inner-walled support body in the guide housing is also too complicated and is also massive (extrusion).

EP 3 020 932 B1 discloses a three-part roller tappet with a solid drive-side and an annular shell-like output-side section. Both sections are coupled in the area of their fronts facing one another via a ring part as a support body (see FIG. 3).

EP 3 173 591 B1 shows a built-up roller tappet with a drive-side guide housing which is plugged together with a roller carrier, on the underside of which an adapter piece for contact with a follower element rests. The adapter piece protrudes beyond the guide housing to an extent that exceeds its height.

Furthermore, DE 10 2017 211 786 A1 discloses a roller tappet with a short design. Its guide housing has two axially successive rings joined together, of which the upper ring receives an insert piece with a pin and roller thereon.

Reference is also made to DE 10 2017 109 761 A1. This shows a roller tappet which is similar to the roller tappet from the first-mentioned DE 10 2017 107 099 B3. The guide housing here consists of two mutually joined, axially directly successive sections. In the joining area, a support body is placed over a radial plate.

DE 10 2016 207 679 A1 discloses an elongated roller tappet with a one-piece guide housing which is assembled with a multi-part support body, which at one end carries a pin with a roller on it and at the other end has a system for a follower member.

Another roller tappet for bridging long installation lengths can be found in

DE 10 2017 107 100 B3.

Finally, reference is made to the “standard design” roller tappet which can be seen in DE 10 2014 218 961 A1.

SUMMARY

The object is to create a roller tappet which is particularly suitable for long installation distances and which is very simple in design and inexpensive to manufacture.

According to the disclosure, this object is achieved in that the two sections of the guide housing are separate, axially spaced rings that are connected to one another via a support body. A drive-side section does not carry a pin with a roller on it. The support body has a first ring area with an upper face and a second ring area with a lower face. The first ring area is connected to an inner jacket of the drive-side section, and the second ring area is connected to an inner jacket of the output-side section. The ring areas of the support body are connected to one another via circumferentially uniformly distributed longitudinal struts on their inner faces. The longitudinal struts lie freely for at least most of their length with respect to the two sections of the guide housing.

Thus, a roller tappet without the above-mentioned disadvantages is provided. It is clear that the tappet can also be used as a roller tappet in valve drives of internal combustion engines and/or can possibly also be present without a roller.

The roller tappet according to the disclosure consists of only very few components reduced to the essential functions. The two sections thereof can be in the form of deep-drawn sheet steel rings. These two sections can be identical, which helps reduce costs. In this case, only the output-side section in the base area has to be designed in such a way that the cross strut or the base remains for the contact of the follower element.

The support body can be produced from sheet steel by stamping and bending, its longitudinal struts being in one piece with the axially spaced ring areas.

By choosing a length of the support struts, different installation lengths can be served with a basic design of the roller tappet. The sections of the guide housing present as rings can optionally be obtained from simple roller bearing rings or from cup tappet base bodies. Under certain circumstances, the roller tappet can also have only one section.

A fixed connection of the sections of the guide housing with the ring areas of the support body can be facilitated by, for example, a welded, riveted, soldered or clipped connection. Alternatively, a press connection is possible.

The roller tappet is particularly light due to the support body, which is largely “exposed” over its length. Tilt-free guidance thus only takes place in the area of its axial end over the two annular sections.

One embodiment of the disclosure relates to the fact that at least the roller-side ring area of the support body is flattened in the circumferential sections of the longitudinal struts, with bores being applied in the flattened sections, in which a pin carrying the roller sits when the roller tappet is fully assembled. This requires two diametrically opposite longitudinal struts. The roller can undergo excellent lateral guidance on the inner surfaces of the flat areas.

It is also useful if, as proposed, the support body is bent together from a sheet steel blank after punching of its basic shape, wherein a bending center here is the imaginary axial line of the support body and roller tappet. End faces of the two ring areas of the support body can, but need not, lie against one another. If necessary, they can also be firmly connected to one another for reasons of rigidity. Here again a welded connection or the like is intended.

Of course, it is conceivable and provided that power is transmitted in the roller tappet directly via its support body (lower face, second ring area) to the follower member. However, it is considered expedient to support the support body on an inner surface of the base or the cross strut of the section on the output side and to act on the follower member via an underside of the base or the cross strut.

A simple measure for anti-rotation locking of the roller tappet in the drive-side section is also described herein. Accordingly, an anti-rotation body such as a needle or a mushroom piece or the like protrudes from an outer jacket of one of the sections. If necessary, this body can also be present as a simple shaping of the respective section.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is explained with reference to the drawings.

FIG. 1 shows a three-dimensional view of the roller tappet, partially broken up; and

FIG. 2 shows the roller tappet in an exploded view.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The figures show a roller tappet 1 for a fuel pump of an internal combustion engine. The roller tappet 1 is suitable for large installation spaces.

The roller tappet 1 has a guide housing 2. This consists of a drive-side and an output-side section 3, 4 of the same external diameter. Both sections 3, 4 are separate and axially spaced rings made of sheet steel. A thin-walled and separate support body 5, likewise made of sheet steel, extends longitudinally through the two-part guide housing 2. The support body 5 carries a roller 9 on its upper face 7 on the drive-side section 3. The latter sits on a pin 21 which is inserted at the end into bores 20 of the support body 5.

It can be seen that the support body 5 has a first ring area 12 with the upper face 7 and a second, axially spaced apart ring area 13 with the lower face 10. The ring areas 12, 13 are welded to the respective inner jackets 14, 15 of the sections 3, 4 and lie within their height. A one-piece connection of the ring areas 12, 13 is established via longitudinal struts 16 which extend from opposing inner faces 17, 18 of the ring areas 12, 13. As can best be seen in FIG. 1, the longitudinal struts 16 of the support body 5 are exposed over most of their length with respect to the sections 3, 4 of the guide housing 2.

The aforementioned bores 20 for the pin 21 in the first ring area 12 lie in the circumferential section of the longitudinal struts 16, which are designed as planar, indented extensions 19. In alignment with these, the upper, drive-side section 3 has two bores 28. As shown in FIG. 1, the pin 21 does not protrude into these bores 28. The pin 21 can, however, sit in the bores 28, which would additionally fix the upper section 3.

From FIG. 2 it can be seen that the support body 5, after punching of its contour, is simply bent around an imaginary center in the blank, which coincides with the axial line of its ring areas 12, 13 and at the same time of the roller tappet 1. End faces 22, 23 of the ring areas 12, 13 run towards one another in the final stage of the bending process, where the end faces 22 of the first, upper ring area 12 adjoin one another.

As can also be seen from FIG. 2, the output-side section 4 of the guide housing 2 is provided in one piece with a transverse strut 25 at its output-side end 24. The areas lying on both sides of the cross brace 25 are punched out. An arrangement 11 for a pump piston is formed on an underside 26 of the cross strut 25. As shown, the second ring area 13 of the support body 5 rests with its lower end 10 on an inner surface 8 of the cross strut 25.

A separate anti-rotation body 6 also protrudes from an outer jacket 27 of the lower, output-side section 4 of the guide housing 2. It has a mushroom-shaped cross-section.

LIST OF REFERENCE CHARACTERS

1 Roller

2 Guide housing

3 Drive-side section

4 Output-side section

5 Support body

6 Anti-rotation body

7 Upper face

8 Inner face

9 Roller

10 Lower face

11 Arrangement

12 First ring area

13 Second ring area

14 Inner jacket

15 Inner jacket

16 Longitudinal strut

17 Inner face

18 Inner face

19 Extension

20 Bore

21 Pin

22 End face

23 End face

24 End

25 Cross brace

26 Underside

27 Outer jacket

28 Bore 

1. A roller tappet for an internal combustion engine, the roller tappet comprising: a guide housing having: a drive-side section, and an output-side section axially spaced and separated from the drive-side section, each of the drive-side section and the output-side section configured with a same outer diameter, a separate support body having: a first end having a first ring area fixedly connected to the drive-side section, the first ring area having a pin configured to receive a roller, a second end having a second ring area fixedly connected to the output-side section, the second ring area arranged to receive a pump piston, and longitudinal struts arranged to fixedly connect the first ring area to the second ring area.
 2. The roller tappet of claim 1, wherein the support body with the longitudinal struts and the first and second ring areas is in one piece and is produced from thin-walled sheet steel by punching and bending.
 3. The roller tappet of claim 1, wherein the first and second ring areas of the support body are connected via two longitudinal struts, and at least the first ring area of the support body is formed with opposed flat, indented extensions, each of the flat, indented extensions: i) adjoined with one of the two longitudinal struts, and ii) having a bore configured to receive the pin.
 4. The roller tappet of claim 1, wherein a first inner jacket of the drive-side section is fixedly connected to the first ring area and a second inner jacket of the output-side section is fixedly connected to the second ring area.
 5. The roller tappet of claim 1, wherein an exposed length of the longitudinal struts of the support body exceeds a sum of a first length of the longitudinal struts covered by the drive-side section and a second length of the longitudinal struts covered by the output-side section
 6. The roller tappet of claim 1, wherein the output-side section of the guide housing is formed with a cross strut, and a lower face of the second ring area abuts with the cross strut.
 7. The roller tappet of claim 1, wherein at least one of the drive-side section or the output-side section of the guide housing is produced from sheet steel.
 8. The roller tappet of claim 1, wherein the drive-side section and the output-side section are welded, riveted, clipped or press-fitted to the corresponding first and second ring areas of the support body.
 9. The roller tappet of claim 1, wherein: the first ring area further comprises a first bore and a second bore, each of the first and second bores configured to receive the pin, and the drive-side section further comprises a third bore aligned with the first bore, and a fourth bore aligned with the second bore.
 10. The roller tappet of claim 1, wherein the output-side section further comprises an anti-rotation body protruding from an outer jacket of the output-side section.
 11. The roller tappet of claim 3, wherein the at least the first ring area further comprises two opposed end faces configured to form a portion of the at least the first ring area arranged outside of the opposed flat, indented extensions.
 12. The roller tappet of claim 11, wherein a first end face of the two opposed end faces is offset from a second end face of the two opposed end faces.
 13. The roller tappet of claim 11, wherein a first end face of the two opposed end faces engages a second end face of the two opposed end faces.
 14. A tappet for an internal combustion engine, the tappet comprising: a drive-side housing, an output-side housing axially spaced and separated from the drive-side housing, the output-side housing and the drive-side housing having a same outer diameter, and a support body having: a first ring area at a first end, the first ring area fixedly connected to the drive-side housing, and a second ring area at a second end, the second ring area fixedly connected to the output-side housing, and at least one longitudinal strut fixedly connecting the first ring area to the second ring area, and the first ring area, the second ring area, and the at least one longitudinal strut are integrally formed from one piece.
 15. The tappet of claim 14, wherein the first ring area, the second ring area, and the at least one longitudinal strut are integrally formed via bending of sheet steel.
 16. The tappet of claim 15, wherein the drive-side housing and the output-side housing are formed as steel rings via a drawing process.
 17. The tappet of claim 16, wherein a first inner jacket of the drive-side housing is fixedly connected to the first ring area and a second inner jacket of the output-side housing is fixedly connected to the second ring area.
 18. The tappet of claim 17, wherein the output-side housing is formed with a transverse strut configured to abut with an end of the support body.
 19. The tappet of claim 17, wherein at least one of the first ring area or the second ring area is formed with two opposed flat, indented extensions configured with bores to receive a pin configured for a roller.
 20. A tappet for an internal combustion engine, the tappet comprising: a drive-side housing ring, an output-side housing ring having a same outer diameter as the drive-side housing ring, and a support body having: a first ring area fixedly connected to the drive-side housing ring, the first ring area having two flat, indented extensions configured to receive a pin configured for a roller, a second ring area fixedly connected to the output-side housing ring and axially offset from the first ring area, and at least one longitudinal strut configured to fixedly connect the first ring area to the second ring area, and the drive-side housing ring is axially offset from the output-side housing ring such that a portion of the at least one longitudinal strut is not surrounded by either of the drive-side housing ring or the output-side housing ring, defining an exposed portion arranged between the drive-side housing ring and the output-side housing ring in a longitudinal direction of the at least one longitudinal strut. 